Lubricating oil compatible polyesters



United States Patent 015 ice Patented Feb. 23, 1965 3,170,898 LUBRICATING OIL CQMPATHBLE PQLYEdTERd Joseph A. Verdol, Bolton, llllL, assignor, by mesne assignments, to Sinclair Research, inc, New York, N.Y., a corporation of Delaware No Drawing. Uriginal application Aug. 7, 1957, er. No. 676,720. Divided and this application Oct. 8, 1959, Ser. No. 848,885

14- (Ilairns. (Cl. 260-75) This invention relates to a new class of compounds which are useful as dispersants in hydrocarbon oils. More particularly, this invention relates to compounds of the polyester type formed by reacting a dibasic acid With an alkyl substituted diethanolamine, said polyesters finding particularly utility as low temperature dispersants in mineral oils of lubricating viscosity.

The use of metallic detergents in internal combustion engine lubricating oil compositions is well known, particular utility for these detergents being found in lubric ating oil compositions which are subjected to heavy duty service resulting in the oxidation of the oil with the resultant formation of sludges and varnishes. Although the metallic detergents such as metallic petroleum sulfonates have been very useful in maintaining these sludge and varnish formations suspended in the oil they have the disadvantage of being themselves subject to breakdown and deterioration resulting in the formation of a metallic ash which accumulates in the combustion chamber. Nor have these metallic detergents proven effective in dispersing the blow-by contamination of the lubricating oil when the engine is operated in light service and at low operating temperatures. When the engine is cold the cylinder walls act as a condenser for the fuel vapors and combustion products in the cylinder. These contaminants wash past or blow-by the piston rings into the crank case wherein they tend to emulsify and coagulate causing insoluble sludge. deposits which the usual meta-llic detergents are usable to redisperse. To overcome these blow-by contaminants and to disperse the sludge deposits in the crank case, attempts have been made to provide ashless dis-persants which will prove effective at the low operating temperatures found in light service internal combustion engines.

In acordance with the present invention, the dispersion of the low temperature sludge deposits can be attained by providing in the mineral lubricating oil base a small but effective amount of the liquid reaction product obtained by reacting approximately equal molar portions of a dibasic acid or an anhydride or ester thereof with an alkyldiethanolamine. The nitrogen-containing polyester thus formed can be added to the lubricating oil base in an amount suflicient to achieve the desired sludge dispersant properties. Generally, the polyester should be added to the base oil in amounts to give about 0.1 to percent or more by weight on the base oil, and preferably, the polyester should be about .75 to 1.5 percent by weight of the base lubricating oil.

The dibasic acids which can be utilized in forming the polyesters of the present invention conform to the following general structural formula:

. HOOCRCOOH wherein R is a divalent, non-aromatic hydrocarbon radical straight or branched, saturated or unsaturated, containing 12 to 38 carbon atoms. By the term non-aromatic in nature, I mean to include not only alipatic hydrocarbon acids but also those acids which are normally monobasic in nature but have been converted to dibasic acids by the cyclization of their hydrocarbon group as Well as cyclic naphthenic dibasic acids. Examples of suitable acids are dodecenylsuccinic, octadecylsuccinic, dimerized unsaturated fatty acids, such as linoleic, ricinoleic, etc. For the purposes of forming the superior low temperature dispersant, however, it is preferred that the dibasic acid be a branched one such as dimerized linoleic acid or dodecenylsuccinic acid. Not only are the dibasic acids useful but also their anhydrides and esters can be employed.

The alkyl substituted diethanolamines useful in preparing the polyesters of the present invention are those in which the alkyl substituent (R') contains from about 4 to 20 carbon atoms. Preferably the alkyl group is straight chained. Examples of useful allcyl diethanolam nes can be enumerated as follows: butyldiethanolamine, octyldiethanolamine, dodecyldiethanolamine, octadecyldiethanolamine, etc.

The polyesters of this invention can be prepared by either of two general methods, i.e. they can be prepared by direct esterification of the dibasic acid or anhydride with the diethanolamine or a dibasic acid ester can be prepared by any of the recognized procedures and the desired polyester prepared by ester interchange between the acid ester and the diethanolamine. The preparations of polyesters found particularly advantageous for use as low temperature dispersants in mineral lubricating oils by each of these two methods are illustrated in the following examples which are not to be considered as limiting. In the example, the reaction providing the detergent additive was continued until the acid number was close to zero, e.g. less than about 1, which is the preferred procedure.

EXAMPLE I Preparation of polyester by direct esterification A mixture of 79.8 grams of dodecenylsuccinic anhydride (0.30 mole) and 91.5 grams of dodecyldiethanolamine (0.30 mole) was placed in a 300 ml. of 4-necked flask equipped with a Claisen head, condenser, thermometer and gas inlet tube through which nitrogen Was bubbled during the reaction period. Approximately 0.2 gram of Zinc stearate was added to the flask as a catalyst. The flask was heated under atmospheric pressure for about three hours at about ZOO-210 C. whereupon 4 mls. of water was collected. The reaction mixture was subsequently heated to 200 C. in vacuum under about 6-10 mm. of pressure for an additional 21 hours. The resultant product was a straw-colored, viscous polymer having the following properties:

Acid No. pH 11 .85 Base No. pH 4 68.00 Percent nitrogen (theory 26) 2.63

A simi ar polyester is obtained by replacing the dodecyldiethanol with octadecyldiethanol or butyldiethanol in an equal molar amount and the products have acid numbers of less than 1.

EXAMPLE 11 Preparation of a polyester by ester interchange A. mixture of 336 grams of the butyl ester of dimerized linoleic acid (about 2 double bonds per molecule) and 80.5 grams of butyldiethanolamine was placed in a 500 m1. 4-neclred flask equipped as described in Example I. 4.16 grams of tetraisopropyl titanate (an ester interchange catalyst) was added to the flask. The mixture was heated under atmospheric pressure in a stream of nitrogen at about 200 C. until 65 grams of butyl alcohol was col; lected. The reaction product was subsequently heated in vacuum for 16 hours at 200 C. The resultant product was a very viscous, amber-colored polymer showing the following properties:

Acid NO. Percent nitrogen (basic) 2.02

It is believed that the above reactions yield polyesters conforming to the following general formula:

R HO R-%OCHZCHZ IG CHQCEZO -H wherein R is as described above, R is the alkyl group of the diethanolamine described above and y is an integer or 1 up to the limit of compatibility of the polyester with the mineral lubricating oil, and preferably, y should be about 5 to 100. Compatibility is used to mean soluble, miscible or otherwise dispersible in the mineral oil without continued agitation and in the amounts required to impart the desired properties to the base oil. Also, in the polyesters R and R should have a total number of carbon atoms of about 22 to 44, preferably more than 30.

The following reactants were polymerized in accordance with the procedures outlined above to obtain polyesters.

The polyesters thus prepared were blended in a solventtreated Mid-Continent neutral mineral oil having a viscosity of 160 SUS at 100 C. The dispersing ability of the oil-soluble polyesters was studied by diluting 50 mls. of the above mineral oil with 50 mls. i kerosene and adding to the blend about 1.0 percent by weight of the additive to be tested. To this blend was added 0.5 gram of carbon black (Benny & Smith carbon black, 24 micron size, pH 3.2). The resultant mixture was homogenized three times through a manually operated homogenizer. The mixture was then heated to about 150 C. and cooled to room temperature. One sample contained no additive and another sample contained 1.0 percent by Weight of du Pont LOA 564, a recognized ashless detergent. The ratings for the carbon black suspension test were made visually with the aid of an optical microscope. The suspension tests were conducted on both dry and wet carbon dispersions. For the wet carbon test, 1 percent by weight water was added by homogenization to the mixture. A summary of these tests is presented in Table 11 following. The additive numbers correspond to those of Table I.

Similarly, additive 3 showed significantly poorer characteristics.

Additives Nos. 2 and 4 were further screened as detergents by conducting suspension tests on the sludge deposits which were collected from the oil pan of a Chevrolet engine which had been run under FL-Z conditions. The lubricating oil composition comprised a solventtreated Mid-Continent neutral lubricating oil having a viscosity of 160 SUS at 100 F. and about 0.7 percent zinc dithiophosphate anti-oxidant. The deposits thus collected were washed several times with pentane by decantation and dried on a suction filter. The thus dried sludge was ground to a fine powder. A 10 percent benzene dis persion of the deposits was prepared by blending 50 gms. of the ground deposit in 50 gms. of benzene and homogenized several times. The sludge suspension tests were carried out by dissolving 1.0 percent by weight of the additives to be tested in 5 mls. of solvent-treated Mid-Continent neutral lubricating oil having a viscosity of 160 SUS at 100 F. and 5 mls. of kerosene. Two mls. of the aboveformed sludge dispersion was then placed in the mixture. After boiling ofli the benzene, the samples were placed in test tubes and permitted to stand several weeks at room temperature. Gne of the thus prepared samples contained no additive and other contained du Pont LOA 564 as a standard of comparison. The amount of agglornerated material was estimated visually with the assistance or: an optical microscope and by an inspection of the settling rates.

In the test sample wherein no additive was used the sludge agglomerated and settled to the bottom almost immediately in the form of a hard cake which was impossible to redisperse by shaking the test tube. The polyesters Nos. 2 and 4 which were effective in the suspension of the carbon black were also found to be just as eiiective in suspending and dispersing the sludge deposits. Although the sludge settled to the bottom of the test tubes having these additives and du Pont LOA 564, respectively, it could be readily redispersed by shaking the test tubes.

In order to evaluate the additives under actual operating condition several blends were prepared and tested under FL-Z Chevrolet engine conditions. These blends were comprised of the following:

(a) Mid-Continent VI neutral lubricating oil having a viscosity of 160 SUS at F. plus about 0.7 percent zinc dithiophosphate.

([1) Composition (a) plus 1.0 percent additive No. l.

(0) Composition (a) plus 1.5 percent additive No. -2.

(d) Composition (0) plus 1.2 percent additive similar TABLE II. CARBON BLACK SUSPENSION TESTS ON VARIOUS DETERGENTS Detergent Additive No.

None

almost immediately. 1% (active ingredient) du Pont LOA 564".--

after several weeks.

Additive No. 1

Additive No. 2

Additive No.3

Additive No. 4 Additive N o. 5

for only two days.

suspended for several we Results Carbon black formed large agglomerates which settled out of oil-kerosene mixture The carbon black remained Microscopic examina- Tests showed this additive to be as good as du Pont LOA 564. Both wet and dry carbon black dispersion containing this additive began to form agglomerates immediately. After one week no carbon black remained suspended.

As can be seen from an examination of this table, the 7 to No. 4 except prepared from dimerized linoleic acid better dispcrsants are formed from the compounds wherein the total carbon atoms in R-l-R' is from 22 to 44 and R has at least 12 carbon atoms. For example, the additive prepared from sebacic acid and octadecyldiethanolamine was not as effective in dispersing and suspending 7 the carbon black as additives 1, 2 and 4 of this invention.

with about one double bond per molecule (Empol 302011).

(e) An SAE 10W-30 oil containing basic barium mahogany sulfonate detergent, zinc dithiophosphate antioxidant, sulfurized sperm oil anti-Wear agent, dimethyl silicone polymer anti-foaming agent, and Acryloid 763 ,4 (T) (a 40 percent concentrate in mineral oil of methacrylate ester polymer in which ester groups are derived from a mixture of alcohols in the C to C range).

(f) Composition (d) plus 1.2 percent additive No. 2. A summary of the engine cleanliness ratings of the above blends is presented in Table III below.

6 is the hydrocarbon portion of dimerized linoleic acid and R is a butyl radical.

5. A polyester compatible with mineral lubricating oils, said polyester being characterized by the formula:

TABLE III Piston Oil Push Push Timing Rocker Blend Skirt Control Oil Rod Rod Gear Arm Rocker Screen Top Tot Average Ring Pan Cgam- Cover Cover Cover Arms Deck Rating 4. 4 9. 5 3. 6. 0 6. O 6. 0 6. 0 9. 10.0 6.0 66. 4 3. 3 8.6 7.0 7.0 8.0 7.0 9.0 9. 5 9.0 9.0 77. 4 4. 4 9.3 3.0 7.0 7.0 6.0 9. 0 9. 5 9.0 8.0 72.2 4. 3 9. l 5.0 7. 0 7.0 6. O 9. 0 9. 0 9.0 9.0 74. 4 3.6 9. 5 8. 0 7.0 7.0 8. 0 8.0 9. 5 10. 0 8. 0 78. 6 4. 8 9. 8 8.0 9.0 8.0 8.0 9. 0 9. 5 10. 0 9. 0 85. 1

The results of these tests indicate that the polyester additives which were effective in the carbon black and sludge suspension tests effectively promote engine cleanliness when the engine is operated under light service conditions. For example, comparing test (a) with (b), (c) and (d), it is seen that the additives promoted the overall engine cleanliness although it was also found that du Pont LOA 564 gave a better rating than additives Nos. 1 and 2. When a metallic detergent is present (test [0] the addition of polyester No. 2 to the blend (test [f]) promoted the low temperature dispersing properties of the lubricating oil.

The lubricating oil base stock used as the major portion in the composition of this invention can be any mineral oil of lubricating viscosity. Frequently, the viscosity of such oils will be from about 50 SUS at 100 F. to 500 SUS at 100 F. If desired, the additives of this invention can be prepared in a small amount of the mineral oil base and stored as a concentrate which can later be blended in the desired portions with the final lubricating oil composition or the additive can be formed and added directly to the lubricating oil. In addition to the polyesters of the present invention other agents can be added to the final composition as desired, for example, pour depressors, VI improvers, other dispersants, antioxidants, foam preventers, anti-corrosive agents, etc. Not only do the polyesters of my invention improve the low temperature dispersant properties of mineral lubricating oils as pointed out above but they are also effective in improving the pour point of the base oil and in raising the viscosity index. Also, the polyester No. 2 of this invention acts as a stabilizer and sludge dispersant in petroleum fuel oils.

This application is a division of my application Serial No. 676,720, filed August 7, 1957.

It is claimed:

1. A polyester compatible with mineral lubricating oils, said polyester being characterized by the formula:

wherein R is selected from the group consisting of aliphatic and cyclic aliphatic divalent hydrocarbon radicals containing 12 to 38 carbon atoms, R is an alkyl radical containing 4 to atoms, R and R contain a total of 22 to 44 carbon atoms and y is an integer from 1 up to the limit of compatibility of the polyester with the mineral lubricating oil.

2. A polyester in accordance with claim 1 wherein R and R contain a total of to '44 carbon atoms.

3. A polyester in accordance with claim 1 wherein R is the hydrocarbon portion of dodecylsuccinic acid and R is an octadecyl radical.

4. A polyester in accordance with claim 1 wherein R wherein R is selected from the group consisting of aliphatic and cyclic aliphatic divalent hydrocarbon radicals containing 12 to 38 carbon atoms, R is an alkyl radical containing 4 to 20 carbon atoms, R and R contain a total of 22 to 44 carbon atoms and y is an integer of from 5 to 100.

6. A polyester in accordance with claim 5 wherein R and R contain a total of 30 [0 44 carbon atoms.

7. A polyester in accordance with claim 5 wherein R is the hydrocarbon portion or" dodecylsuccinic acid and R is an octadecyl radical.

8. A polyester in accordance with claim 5 wherein R is the hydrocarbon portion of dimerized linoleic acid and R is a butyl radical.

9. A method for producing a polyester compatible with mineral lubricating oils, said polyester being characterized by the formula:

H0(( i-R OOHgCHzI ICH2CHz0 -H wherein R is selected from the group consisting of aliphatic and cyclic aliphatic divalent hydrocarbon radicals containing 12 to 38 carbon atoms, R is an alkyl radical containing 4 to 20 atoms, R and R contain a total of 22 to 44 carbon atoms and y is an integer from 1 up to the limit of compatibility of the polyester with the mineral lubricating oil, which comprises reacting approximately equimolar portions of an alkyl diethanol amine of the formula 0 II o and a member selected from the group consisting of dibasic acids of the formula HOOCRCOOH and their esters and anhydrides to produce said oil-compatible polyester.

10. The method of claim 9 in which y is an integer from 5 to 100.

11. The method of claim 9 in which the reaction is continued to give a product having an acid number of less than 1.

12. The method in accordance with claim 11 wherein R and R contain a total of 30 to 44 carbon atoms.

13. The method in accordance with claim 11 wherein R is the hydrocarbon portion of dodecylsuccinic acid and R is an octadecyl radical.

14. The method in accordance with claim 11 wherein R is the hydrocarbon portion of dirnerized linoleic acid and R is a butyl radical.

References Cited in the file of this patent UNITED STATES PATENTS 2,094,608 Kritchevsky June 8, 1936 2,343,436 Wells Mar. 7, 1944 2,430,004 De Groote et a1 Nov. 4, 1947 2,733,169 Holmen Jan. 31, 1956 

1. A POLYESTER COMPATIBLE WITH MINERAL LUBRICATING OILS, SAID POLYESTER BEING CHARACTERIZED BY THE FORMULA: 